The invention relates to protective devices, and more particularly relates to protective devices which protect electrical equipment and those who use it from electrostatic discharge. In its most inmmediate sense, the invention relates to an electrostatic discharge protection device for use in telephone keysets.
Electrostatic discharge is often encountered with, e.g., telephone keysets and other electronic devices that are used in the home or in the office. Where a user accumulates an electrostatic charge by walking on carpeting or by sitting on upholstered furniture, the charge may be dissipated through, e.g., a telephone keyset when the user picks up the receiver. Because relatively high electrostatic voltages can be built up, electrostatic discharge can be painful because the discharge current can be relatively high. Furthermore, such high currents can generate strong electromagnetic fields; these can induce voltages in sensitive electronic equipment and damage it.
Originally, attempts to reduce the current produced during electrostatic discharge were directed to increasing the dielectric strength of the housing of, e.g. telephone keysets. Such results can be obtained by, e.g. using intermediate layers of insulation and thereby increasing the distance between the sensitive electronic circuitry and the user's hand. However, such attempts have proved unsatisfactory because high electrostatic voltages require entirely new housing structures.
It would be advantageous to provide a device which would protect both a piece of electronic equipment and the user of such equipment from electrostatic discharge.